INTERACTION OF β-LACTAMASE OF STREPTOMYCES CACAOI: II. CP-45, 899, IZUMENOLIDE AND CEPHAMYCINS

Inhibition of a β-lactamase of Streptomyces cacaoi by CP-45, 899, izumenolide and cephamycins was investigated and compared with that of a β-lactamase of Bacillus cereus. S. cacaoi enzyme could not hydrolyze CP-45, 899. Instead, hydrolysis of benzylpenicillin by the enzyme was inhibited in the presence of CP-45, 899. Although inhibition increased gradually with time, the inhibition line produced by CP-45, 899 with time was less curved than that produced by clavulanic acid and PS-5. Furthermore, preincubation of S. cacaoi β-lactamase with CP-45, 899 for up to 120 seconds did not obviously affect the degree of inhibition. When the concentration was lowered, it behaved as a competitive inhibitor, a Ki value being 6.2×10-7 M. Izumenolide, on the other hand, did not inhibit the enzyme activity of S. cacaoi β-lactamase at 1.28×10-4M, although it inhibited B. cereus enzyme slightly in a competitive manner. Oganomycins were inert to the both β-lactamases.